Thermoplastic polyamides are widespreadly used as engineering plastics, mainly in the manufacture of automotive and electronic components and in the field of packaging. For these applications, it is often required that the polyamides have high hydro- and oleo-phobilcity and that they also show low brittleness, i.e. low tendency to crack, especially when the polyamides are exposed to cold temperatures or mechanical stress. In order to reduce brittleness, either additives, in particular plasticizers (or impact modifiers), can be blended with the finished polyamide or polymerization can be carried out in the presence of comonomers that are able to reduce the Tg of the polyamide. However, the insertion of additives or the use of certain comonomers may alter or reduce other properties which would instead be desirable to retain or even increase, including hydro- and oleo-phobicity. Thus, it is generally difficult to improve all aforementioned properties by blending with additives or insertion of comonomers. There is therefore the need to provide thermoplastic polyamides showing increased chemical resistance and surface properties in combination with reduced brittleness, said polyamides not requiring being blended with additives, in particular plasticizers.
It is known that (per)fluoropolyethers (herein after “PFPEs”) can be used as additives for other polymers in order to modify certain physical/chemical properties of the polymer concerned. It has been observed that, when PFPEs are physically blended to other polymers, they tend to segregate and to migrate to the surface during polymer processing; in some instances, the separation of the PFPE from the composition might reduce the durability of the composition and of the finished article obtained therefrom. Moreover and more important, in several applications (e.g. biomedical applications), the risk of separation of chemical components from compositions represents a toxicological concern, so the use of additives is not acceptable.
PFPEs can also be used as co-macromers in the course of polymerization, thereby obtaining modified polymers having a PFPE covalently bound thereto. For example, patent documents EP 1864685 A (SOLVAY SOLEXIS S.P.A.), U.S. Pat. No. 5,476,910 (AUSIMONT S.P.A.), U.S. Pat. No. 5,686,522 (AUSIMONT S.P.A.) and U.S. Pat. No. 5,109,103 (AUSIMONT S.P.A.) disclose polyurethanes (PUs), polyurethane/polyesters (PUs/PEs) or polyesters (PEs) that are modified with PFPEs.
Patent documents U.S. Pat. No. 6,127,498 (AUSIMONT S.P.A.), WO 2009/010533 (SOLVAY SOLEXIS S.P.A.) and U.S. Pat. No. 5,508,380 (AUSIMONT S.P.A.) relate to other polymers or polymer additives modified with PFPE segments or blocks; modified polymers containing PFPE segments or blocks and amido moieties are generically mentioned.
U.S. Pat. No. 3,876,617 (MONTEDISON S.P.A.) discloses elastomeric polyamides and copolyamides which can be obtained by reacting a PFPE diacid, preferably in the form of a reactive derivative, with a diamine. In particular, in U.S. Pat. No. 3,876,617 it is stated that the polyamides can also contain further monomeric units with more than two functions, like polycarboxylic acids, to an extent up to 30% in number with respect to the bifunctional units. The amount of PFPE diacid contained in these polyamides is high and, for this reason, the resulting polyamide is endowed with elastomeric properties. Furthermore, this document does not specifically disclose polyamides obtained by reaction of a PFPE diacid, a diamine and a polycarboxylic acid.
WO 2010/049365 (SOLVAY SOLEXIS S.P.A.) relates to polymers comprising PFPE segments as additives for hydrogenated polymers to give them good surface properties, in particular a low coefficient of friction (page 1, lines 1-3). This document discloses, inter alia, polyamide additives which can be obtained by reacting a non-fluorinated diamine with a PFPE having ester or carboxyl functionality, in an amount in equivalent of amino groups equal to that of the functional groups of the diamine (see page 10, lines 5 to 8).
WO 2011/082063 A (3M INNOVATIVE PROPERTIES COMPANY [US]) discloses copolymers comprising at least one PFPE segment, at least one polydiorganosiloxane segment and multiple aminooxyalkylamino groups of formula (XI):
wherein:                Q1 contains a PFPE segment;        Q2 contains a polydiorganosiloxane segment;        each R2 is independently hydrogen, alkyl, aralkyl or aryl, each variable q, p and m is independently an integer to at least 1 and        each asterisk denotes a site of attachment to another group in the copolymer.        
WO 2011/082046 A (3M INNOVATIVE PROPERTIES COMPANY [US]) discloses copolymers of formula (IV)
wherein:                each group Q1 contains a perfluoropolyether segment;        each group Q is (a) an alkylene, (b) fluorinated alkylene, (c) heteroalkylene, (d) arylene, (e) a carbonylamino group linking a first group to a second group, wherein the first group and the second group are each independently an alkylene, fluorinated alkylene, heteroalkylene, arylene, a combination thereof, (f) part of a heterocyclic group that includes R7 and a nitrogen to which R7 is attached, or (g) a combination thereof;        each R2 is independently hydrogen, alkyl, aralkyl, or aryl;        each R7 is independently hydrogen, alkyl, aralkyl, aryl, or part of a heterocyclic group that includes Q and a nitrogen to which R7 is attached;        each variable q, p, and m is an integer equal to at least 1;        each asterisk denotes a site of attachment to another group in the copolymer.        